This invention relates in general to aircraft control systems and in particular to a control for a rotor aircraft for desensitizing movement of the control stick relative to tilt of the rotor at higher speeds.
U.S. Pat. No. 5,727,754 discloses a rotor aircraft that has a fuselage, a rotor mounted to a tiltable spindle, wings extending from the fuselage and a propeller for propelling the aircraft in forward flight. A clutch connects the rotor to the engine to spin the rotor while the aircraft is still on the ground. As the aircraft begins to lift, the clutch mechanism releases the rotor from the engine and the rotor continues to spin due to its momentum. The propeller pushes the aircraft at the same time causing the wings to begin developing lift. As the aircraft speeds up, the rotor is tilted forward causing less airflow through the rotor, with the wings sustaining more of the load. Forward flight causes the rotor to free wheel.
The patent discloses a control stick for tilting the rotor forward, rearward and lateral directions. A control stick also controls a horizontal stabilizer. At a selected forward flight speed, a wrist control mounted on top of the main control stick is tilted forward. The wrist control moves tilts the rotor and the horizontal stabilizer at or close to the same rate and in the same direction so that the angle between them stay essentially constant. While workable, improvements are desired.
The control system of this invention has a linkage assembly connected between the control stick and the spindle for tilting the spindle in fore and aft directions in response to movement of the control stick. An adjusting member is member is movable between first and second positions to reposition at least portions of the linkage assembly relative to the control stick between gross and fine positions. In the fine position, the linkage assembly desensitizes the control stick so that a selected fore and aft movement of the control stick causes less tilting movement of the spindle than while in the gross position.
This is accomplished by having a control point in the linkage assembly that rotates about a pivot point of the control stick at a selected radius. The adjusting member will vary the radius, which in turn changes the tilting response of the rotor spindle. A smaller radius will result in a substantially smaller tilting movement of the rotor spindle for full aft to full forward movement of the control stick.
The adjusting member does not affect other movements caused by the control stick. The horizontal stabilizer, mounted at the aft of the end of the fuselage, is connected to the control stick so that forward movement of the control stick causes downward tilting of the horizontal stabilizer. Full forward and aft movement of the control stick results in full downward and forward tilting of the horizontal stabilizer regardless of the position of the adjusting member.
Also, lateral movement of the control stick tilt the rotor spindle laterally as well as pivoting ailerons mounted to the wings. The tilting movement is not affected by any position of the adjusting member.